Well, if you were trapped in ice, I imagine the ice had something to do with it.

[ The not aging part.

Though, Kakashi's still not sure how on earth Steve hadn't died in such conditions. Serum or not, such a thing should have killed him. Being frozen to death is, after all, as effective as a projectile through the head. Logically, anyway. He almost suspects that Steve can't be killed, despite what the other says. ]

Either way, I'm glad you survived.